Engine management and control systems are important components of present day road vehicles as they have a vital impact on fuel economy and reduced emissions. Engine developers want to run the ECU while monitoring its internal state through special programs, after changing part of the ECU code or tables in it, to make sure that everything is in order. Hardware in the loop test systems are used to supply the necessary sensor signals to the ECU during such tests. This paper presents a low cost, portable engine ECU hardware-in-the-loop simulation system that uses a PC card in a laptop computer for supplying the necessary crank and camshaft sensor signals. The signals are generated in a Simulink (R) program which can also accommodate simple engine models.